1. Field of the Invention
The present invention pertains to an apparatus for measuring the vapor pressure of various liquids, particularly complex hydrocarbon mixtures.
2. Background
It is often necessary to determine the vapor pressure of a liquid or liquid mixture to assist in controlling transport conditions of the liquid or certain process conditions involving the liquid or its vapor. In many crude oil pipelining operations, it is desirable and often necessary to transport other liquids mixed with the crude oil, such as, natural gasoline liquids. Accordingly, a relatively complex liquid mixture is formed under such transport conditions and the vapor pressure of such a mixture cannot be readily predicted but can only be determined by frequent measurements of the fluid being transported through the pipeline. Moreover, the true vapor pressure of a complex liquid mixture such as a mixture of crude oil and natural gasoline liquids may actually be a changing value since the vapor pressure of the so called lighter ends of the mixture will be lower at a given temperature than the heavier or more dense hydrocarbon materials.
Accordingly, it has been deemed desirable to provide an apparatus which can readily measure at least the cavitation pressure of a complex liquid mixture so that pumping operations and the like may be controlled to prevent cavitation and leakage of vapors from the transport network. On the other hand, knowledge of the true vapor pressure is important for certain processing or separating operations.
It is an object of the present invention to provide an improved apparatus and method for determining the cavitation pressure of a pure or complex liquid mixture as well as the vapor pressure of the mixture with accuracy and in a manner which provides for sampling the liquid mixture to be measured at will. Other objects, advantages, and superior features of the present invention are described hereinbelow.